Toothed rotor piston machine

ABSTRACT

Rotary piston machines have a casing with two intersecting cylindrical bores in which a main rotor and a gate rotor are mounted for rotation. Each rotor has a hub and one tooth with a concave flank extending from the hub and a recess adjacent said flank. The rotors define with the bore walls a working chamber for an elastic fluid quantity which changes volume during rotation. The torque produced by fluid pressure on a rotor tooth is directed in the same direction during a complete rotation and working cycle of the machine due to the shape of the main rotor tooth.

United States Patent 1 Persson TOOTHED ROTOR PISTON MACHINE [75] Inventor:

[73] Assignee: Atlas Copco Aktiebolag, Nacka,

Sweden [22] Filed: July 14, 1972 [21] Appl. No.: 271,981

Related US. Application Data [63] Continuation of Ser. No. 44,738, June 9, 1970,

abandoned.

Jan Edvard Persson, Ektorp, Sweden [30] Foreign Application Priority Data June 18, 1969 Sweden 8636/69 [52] U.S. Cl. 418/191 [51] Int. Cl. F01c 1/08, F040 1/14, F04c 17/04 [58] Field of Search 418/189, 190, 191,

[56] References Cited UNITED STATES PATENTS 10/1969 Brown ..4l8/189 10/1970 Brown ..418/191 11] 3,748,069 July 24, 1973 2,097,037 10/1937 Northey 418/206 2,724,340 11/1955 Tryhom 418/190 FOREIGN PATENTS OR APPLICATIONS 492,024 9/1938 Great Britain 418/ 191 734,691 8/1943 Germany 418/191 Primary Examiner-Carlton R. Croyle Assistant Examiner-John J. Vrablik Attorney-Eric Y. Munson [57] ABSTRACT Rotary piston machines have a casing with two intersecting cylindrical bores in which a main rotor and a gate rotor are mounted for rotation. Each rotor has a hub and one tooth with a concave flank extending from the hub and a recess adjacent said flank. The rotors define with the bore walls a working chamber for an elastic fluid quantity which changes volume during rotation. The torque produced by fluid pressure on a rotor tooth is directed in the same direction during a complete rotation and working cycle of the machine due to the shape of the main rotor tooth.

4 Claims, 7 Drawing Figures Patented July 24, 1973 6 Sheets-Sheet 1 JAN EDVARD PERSSON IN VENTOR.

MUNSON & :FIDDLER,

Attorneys.

Patented July 24, 1973 3,748,069

6 Sheets-Sheet 2 JAN EDVARD PERSSON BY- MUNSON & FIDDLER,

Attorneys.

Patented July 24, 1973 6 Sheets-Sheet 5 Fig. 3

JAN IIDVARI) PERSSON IN Vlz'N'lfUR.

MUNSON & FIDDLER,

Attorneys Patented July 24, 1973 6 Sheets-Sheet 4 JAN EDVARD PERSSON INVISN'I'OR.

MUNSON & FIDDLER,

Attorneys Patented July 24, 1973 3,748,069

6 Sheets-Sheet 5 JAN EDVARD PERSSON BY MUNSON & FIDDLER,

Attorneys.

Patented July 24, 1973 6 Sheets-Sheet 6 JAN EDVARD PERSSON IN VENTOR.

BY MUNSON & FIDDLER,

Attorneys TOOTIIED ROTOR PISTON MACHINE This application is a continuation of copending application Ser. No. 44,738 filed June 9, 1970 and now abandoned.

This invention relates to rotary machines with toothed rotors and of the type having a main rotor and a gate rotor provided each per se with a hub having a hub portion with substantially constant radius and with a tooth, said tooth on the main rotor having a concave flank and a convex flank, said convex flank merging into said hub portion of the main rotor, said tooth on the gate rotor having at least a concave flank and a second flank, said second flank merging into the hub portion of the gate rotor, said hub on the main rotor having a recess adjacent said concave flank of the main rotor tooth for the passage of the gate rotor tooth, said hub on the gate rotor having a recess adjacent said concave flank of the gate rotor tooth for the passage of the main rotor tooth, and said machine having a casing with intersecting cylindrical bores, one for each rotor, and end walls formed with axial inlet and outlet ports for an elastic working fluid, said rotors being mounted for rotation in said bores in said casing with the teeth in sealing proximity to the bores and end walls for positive displacement and change of volume of quantities of working fluid moving through the machine at each working cycle, and said machine having means for synchronizing the rotation of the rotors. One object of this invention is to provide a rotary piston machine of the type described, in which the torque produced by pressure of the working fluid on the rotary pistons has the same direction during a complete working cycle of the machine. Another object of this invention is to provide a rotary piston machine which has high capacity in relation to the external dimensions of the machine and particularly the machine casing. A further object of the present invention is to provide a rotary piston machine of the typedescribed in which the lengthof the leakage or sealing linesas compared with the swept cylinder volume of the machine is a minimum. A still further object of the invention is to provide in rotary piston ma chines of the type described inlet and outlet ports which are as large as possible. A further object of the invention is to provide a rotary piston machine of the type described in which the velocity of the working fluid in the machine and in the inand outlet ports is low. A still further object of the invention is to provide a rotary piston machine of the type described which has relatively large intake volume. A still further object of the invention is to provide a rotary piston machine with low discharge temperature of the discharged working fluid when the machine is operated as a compressor.

The rotary piston machine of the type described hereinabove is substantially characterized by the fact that the main and gate rotor teeth form a seal with the bores and end walls of the casing during the main part of each revolution and that the concave flank of the gate rotor tooth and a portion of the gate rotor hub defining the recess for the main rotor tooth are generated by the main rotor tooth tip and the convex main rotor tooth flank, respectively, to such shapes that during the minor part of each revolution when the rotor tooth of each rotor cooperates with the rotor tooth and recess of the other rotor a sealing line between the main rotor tooth tip and the generated concave flank of the gate rotor tooth is always situated more remote from the axis of rotation of the gate rotor than the sealing line between the convex main rotor tooth flank and said portion of the gate rotor hub defining said recess, so

that the torque of the fluid pressure acting on the rotor said contour portions define the gate rotor recess and together with the concave gate rotor tooth flank form a contour with a single inflection point, which simplifies manufacture.

The capacity of a machine with one tooth on each rotor is higher than in machines with two or more teeth since in the latter a considerable volume of the machine is used for transportation of working fluid instead of for useful work. The rotary piston machine according to the invention is primarily intended to operate as a compressor but may also be carried out so as to operate as a motor.

In the accompanying drawings one embodiment of a rotary piston machine according to the invention carried out as a compressor is illustrated by way of example together with a modification.

FIG. 1 is an end view of a rotary piston compressor according to the invention with one tooth on each rotor. FIG. 2 is a cross section of the compressor in'which, however, the rotors are. illustrated in end view.

FIG. 3 is a longitudinal axial section on. a plane through the rotor axes on line III-III in FIG. 1.

FIG. 4 is an end view of the cooperating main and gate rotors of the machine in FIGS. 1 3.

FIGS. 5 and 6 are detail' views on a reduced scale somewhat diagrammatic illustrating the rotors and contours of the cylinder bores, as viewed from one end of the rotors in the moment when compressionstarts and the moment when discharge starts, respectively.

FIG. 7 is a view similar to FIG. 4 with the two rotors in a position where the tooth tips of the rotors have just met said rotors being somewhat modified with regard to the rotors illustrated in FIGS. 2 and 4 6.

The rotary piston machine illustrated in FIGS. 1 7

is a single stage tooth compressor provided with a main rotor and a gate rotor each per se provided with one tooth. The machine is provided with a casing which consists of, a central compressor housing 1 provided with two end walls 2, 3 which are bolted to the central compressor housing I by means of bolts 4. The housing 1 is provided with two cylindrical intersecting bores 5, 6 with parallel axes which bores intersect to a certain degree. The bores S, 6 and end walls 2, 3 form working chambers for main rotor 7 and a gate rotor 8 which rotors are provided and secured on parallel shafts 9 and 10, respectively, which are mounted for rotation in bearings in the end walls 2, 3 and synchronized by means of a toothed gear transmission 12 and sealed towards the working chambers in the housing 1 by sealing rings 13. The housing 1 is provided with an inlet conduit portion 14 and an outlet conduit portion 15 which two portions end up in plane's I6 and 17 which are perpendicular one to the other and parallel with the rotor axis. A passage 18 from the conduit portion 14 leads through the end walls 2 and 3 and the housing 1 to inlet ports for the working chamber of the machine which inlet port consists of a radial inlet port portion 19 and two axial inlet port portions 20 one in each end wall. The outlet conduit portion 15 is through an outlet passage 21 in the housing 1 and the end walls 2, 3 connected to two axial high pressure ports 22 one in each end wall. The housing 1 is air cooled and the end walls 2, 3 are liquid cooled and are for this purpose provided with liquid cooling fluid passages 23 and passages 24 for draining cooling fluid from the transmission housing 34.

The main rotor 7 has a hub with a hub portion 25 with constant radius which in the illustrated embodiment extends through an angle of 225 of the periphery of the main rotor hub. The main rotor hub, furthermore, carries a tooth 26 which has a leading convex flank which is formed by a flat portion 27 which connects the hub portion 25 with constant radius with a preferably circularly arcuate portion 28 which extends to the tip 29 of the tooth. The trailing flank of the main rotor tooth 30 is concave and disposed immediately adjacent a recess 31 which is formed in the hub and extends to and merges into the hub portion 25.

The main rotor 7 has a cavity 32 which extends into the main rotor from an opening 33 in the trailing concave flank 30 of the main rotor tooth, said opening extending over the main part of said flank. The cavity 32 is shaped in such a manner that the main rotor is dynamically and naturally also statically balanced.

The relation between the constant radius of the hub portion 25 of the main rotor and the maximum radius of the main rotor tooth 26 is in the illustrated embodiment 35 to 60. Preferably, the maximum radius of the main rotor tooth may be 50 to 100 percent larger than the constant radius of the hub portion 25 of the main rotor. The length of the main rotor may preferably be substantially equal to the maximum radius. The invention results in a very favourable utilization of the volume of the compressor casing. Furthermore, a favourable relation between the total sealing line length and the swept volume of the machine is obtained which involves small leakage losses.

The gate rotor 8 has a hub with a hub portion 35 with constant radius which in the illustrated embodiment extends over an angle of 225 of the periphery of the gate rotor and cooperates with the hub portion 25 with constant radius of the main rotor and seals against said portion. However, upon rotation of the rotors the peripheral speed of the main rotor hub portion differs from the peripheral speed of the gate rotor hub portion. This difference causes a suitable wear of the rotor surfaces which results in a suitable sealing clearance. The gate rotor has a tooth 36 with a leadingconcave flank 37 generated by the tip 29 of the tooth 26 of the main rotor during the movement of said tip from the tip 38 of the gate rotor tooth to the root of said tooth. The leading flank 37 of the gate rotor tooth 36 merges at the root of the tooth in a portion 39 which is an envelop to a family of circles generated by the circular are shaped portion 28 of the main rotor tooth on the gate rotor. The envelop portion 39 merges into the hub portion 35 via a portion 40 which is generated by the portion 27 of the main rotor tooth and which is consequently an envelop of a family of lines. The gate rotor tooth 36 has a portion 41 at the tooth tip which is shaped as a circular arc and extends from the tip 38 of the tooth and merges into the trailing flank 42 of the gate rotor which is a tangent to the hub portion 35 and may have any suitable shape within certain limits, since it does not have to form a seal with the main rotor. The tips 38, 29 of the respective teeth may be rounded as obvious from FIG. 7 so that they are not so easily damaged and produce a better seal with the respective cooperating rotor portion. The tip 38 of the gate rotor tooth, the circularly are shaped portion 41 and the trailing flank 42 have generated the trailing flank 30 of the main rotor tooth and the recess 31 in the main rotor hub but these portions which extend over an arc of 45 of the rotors do not jointly have to form a seal.

Since the gate rotor is also asymmetric it has, similarly to the main rotor, been provided with a cavity 43 which extends into the gate rotor from an opening 44 in the trailing flank 42 of the gate rotor tooth. The effective height of the gate rotor tooth is in the illustrated embodiment about one third of the effective height of the main rotor tooth. By this arrangement and this relation between the heights of the teeth it is possible to carry out the outlet ports so large that the air or gas velocity in these ports stay within reasonable limits and the flow velocities are thereby kept down. Similarly more suitable fluid velocity is obtained in the passages which surround the rotor in the compressor housing.

In order to make this operation of the machine more obvious and clear, the rotors in FIGS. 5 and 6 have been illustrated in the positions which they take when the compression starts as in FIG. 5 and when the discharge starts as in FIG. 6. FIG. 7 which illustrates the modification with rounded rotor tips also illustrates the position of the rotors at the moment when the tips 29, 38 meet. The distance or gate rotor radius to the sealing line between the tip 29 and the flank 37 should in all positions of the rotors be larger than the radius to the sealing line between the convex flank 27, 28 and the hub portion 40, so that the torque of the fluid pressure on the gate rotor tooth is always positive. The di-' rection of rotation of the rotors is illustrated by arrows in FIGS. 1, 2, 5 and 6 and' is the same also in FIGS. 4 and 7. FIG. 7 illustrates the rotors in the position they take when the tip 29 and 38 of the rotor teeth have just arrived into cooperating position where the tooth tip 29 starts to sweep the surface 37 of the tooth 36 in sealing proximity the clearance at the tooth tip 29 in FIG. 7 being somewhat exaggerated. In order to improve the sealing around the rotors, the convex peripheral surfaces of the rotors may preferably be provided with a coating of a material which may be partly worn away, for instance paint. The end surfaces or end walls of the cylinder bores which are directed towards the rotors may also be provided with such surface coating.

The rotor machines described hereinabove should only be considered as examples and may be modified and varied in several different ways within the scope of the following claims.

I claim:

1. In a rotary piston machine for handling a working fluid comprising the combination of:

a. a main rotor and a gate rotor each of said rotors having a hub portion with a substantially constant radius with a tooth projecting from each of said hub portions;

b. a casing having cylindrical intersecting bores rotatably supporting said rotors, end walls bounding said bores axially and low and high pressure ports for passing the working fluid into said bores;

c. said rotors being rotatable in said bores with the teeth in sealing proximity to the walls thereof for positive displacement and change of volume of working fluid moving through the machine during each working cycle;

. thetooth on the main rotor having a tip and a concave flank and a convex flank, the convex flank merging with the hub portion;

e. the tooth of the gate rotor having a concave flank generated by the main rotor tooth tip and a second flank, said second flank merging with the hub portion;

f. the hub portion of each rotor having a recess located adjacent the concave flank of its respective tooth to permit interengagement when the rotors are rotated;

. the recess of said gate rotor being defined by convex contour portion extending from the hub portion and merging with a concave contour portion which in turn merges with the concave flank of the gate rotor; 7

h. the hub portion of the gate rotor controlling the high pressure port;

i. the rotors having such profiles as to seal the bores and the end walls of the casing during the main part of each revolution and so as to cause the concave flank of the gate rotor tooth and said recess defining convex and concave contour portions to be generated by said main rotor tooth and the convex flank thereof along a sweep of substantially 90 of the periphery of the gate rotor, the concave flank of the gate rotor tooth and said convex and concave contours forming together combined concave and convex contour portions having a single inflection point;

j. said profiles further being such that a first sealing line is formed between the main rotor tooth tip and the generated concave flank of the gate rotor tooth and a portion of said concave contour portion of the gate rotor hub during the minor part of each revolution when the teeth -interengage,'said first sealing line being located farther remote from the axis of rotation of the gate rotor than a second sealing line formed between the convex flank of the main rotor tooth and said recess defining contour portions which are generated by the convex main rotor tooth flank, and I I k. the profiles of said rotors being calibrated so that a compressed fluid space communicating with the high pressure port will be located between the concave flank of the gate rotor tooth and the convex flank of the main rotor tooth when the teeth interengage and said sealing lines move and until the sealing lines intersect, whereby the torque of the fluid pressure acting on said rotors during each revolution is maintained in the same direction during a complete working cycle of the machine.

2. A rotary'machine according to claim 1, in which the convex main rotor leading tooth flank comprises a convex contour portion extending from the tooth tip and merging with the substantially constant radius hub portion through a flat contour portion, which is tangent to said convex contour portion and said hub portion.

3. In a rotary piston machine for handling a working fluid comprising the combination of:

a. a main rotor and a gate rotor each of said rotors having a hub portion with a constant radius over a substantial portion of the hub periphery and with a tooth projecting from each of said hub portions;

b. a casing having cylindrical intersecting bores rotatably supporting said rotors, end walls bounding said bores axially and low and high pressure ports for passing the working fluid into said bores;

c. said rotors being rotatable in said bores with the teethin sealing proximity to the walls thereof for positive displacement and change of volume of working fluid moving through the machine during each working cycle;

d. the tooth on the main rotor having a tip and a first flankand a second flank, said second flank having a convex portion and a portion merging with the hub portion;

e. the tooth of the gate rotor having a concave flank generated by the main rotor tooth tip and a second flank, said second flank merging with the hub portion; the hub portion of each rotor having a recess located adjacent a tooth flank to permit interengagement when the rotors are rotated;

. the recess of said gate rotor being defined by a convex contour portion extending from the hub portion and merging with a concave contour portion which in turn merges with the concave flank of the gate rotor;

h. the hub portion of the gate rotor controlling the high pressure port;

i. the rotors having such profiles as to seal the bores and the end walls of the casing during the main part of each revolution and so as to cause the concave flank of the gate rotor tooth and said recess defining convex and concave contour portions to be generated by said main rotor tooth and the convex flank portions thereof along a sweepof substantially of the periphery of the gate rotor, the concave flank of the gate rotor tooth and said convex and concave flank of the gate rotor tooth and said convex and concave contours forming together combined concave and convex contour portions having a single inflection point;

j. said profiles further being such that a first sealing line is formed between the main rotor tooth tip and the generated concave flank of thegate rotor tooth and a portion of said concave contour portion of the gate rotor hub during the minor part of each revolution when the teeth interengage, said first sealing line being located farther remote from the axis of rotation of the gate rotor than a second sealing line formed between the convex flankof the main rotor tooth and said recess defining contour portions which are generated by the convex main rotor tooth flank, and

k. the profiles of said rotors being calibrated so that a compressed fluid space communicating with the high pressure port will be located between the concave flank of the gate rotor tooth and the convex flank of the main rotor tooth when the teeth interengage and said sealing lines move and until the sealing lines intersect, whereby the torque of the fluid pressure acting on said rotors during each revolution is maintained in the same direction during a complete working cycle of the machine. I

4. A rotary machine according to claim 3, in which the convex main rotor leading tooth flank comprises a convex contour portion extending from the tooth tip and merging with the substantially constant radius hub portion through a flat contour portion, which is tangent to said convex contour portion and said hub portion.

* III 

1. In a rotary piston machine for handling a working fluid comprising the combination of: a. a main rotor and a gate rotor each of said rotors having a hub portion with a substantially constant radius with a tooth projecting from each of said hub portions; b. a casing having cylindrical intersecting bores rotatably supporting said rotors, end walls bounding said bores axially and low and high pressure ports for passing the working fluid into said bores; c. said rotors being rotatable in said bores with the teeth in sealing proximity to the walls thereof for positive displacement and change of volume of working fluid moving through the machine during each working cycle; d. the tooth on the main rotor having a tip and a concave flank and a convex flank, the convex flank merging with the hub portion; e. the tooth of the gate rotor having a concave flank generated by the main rotor tooth tip and a second flank, said second flank merging with the hub portion; f. the hub portion of each rotor having a recess located adjacent the concave flank of its respective tooth to permit interengagement when the rotors are rotated; g. the recess of said gate rotor being defined by convex contour portion extending from the hub portion and merging with a concave contour portion which in turn merges with the concave flank of the gate rotor; h. the hub portion of the gate rotor controlling the high pressure port; i. the rotors having such profiles as to seal the bores and the end walls of the casing during the main part of each revolution and so as to cause the concave flank of the gate rotor tooth and said recess defining convex and concave contour portions to be generated by said main rotor tooth and the convex flank thereof along a sweep of substantially 90* of the periphery of the gate rotor, the concave flank of the gate rotor tooth and said convex and concave contours forming together combined concave and convex contour portions having a single inflection point; j. said profiles further being such that a first sealing line is formed between the main rotor tooth tip and the generated concave flank of the gate rotor tooth and a portion of said concave contour portion of the gate rotor hub during the minor part of each revolution when the teeth interengage, said first sealing line being located farther remote from the axis of rotation of the gate rotor than a second sealing line formed between the convex flank of the main rotor tooth and said recess defining contour portions which are generated by the convex main rotor tooth flank, and k. the profiles of said rotors being calibrated so that a compressed fluid space communicating with the high pressure port will be located between the concave flank of the gate rotor tooth and the convex flank of the main rotor tooth when the teeth interengage and said sealing lines move and until the sealing lines intersect, whereby the torque of the fluid pressure acting on said rotors during each revolution is maintained in the same direction during a complete working cycle of the machine.
 2. A rotary machine according to claim 1, in which the convex main rotor leading tooth flank comprises a convex contour portion extending from the tooth tip and merging with the substantially constant radius hub portion through a flat contour portion, which is tangent to said convex contour portion and said hub portion.
 3. In a rotary piston machine for handling a working fluid comprising the combination of: a. a main rotor and a gate rotor each of said rotors having a hub portion with a constant radius over a substantial portion of the hub periphery and with a tooth projecting from each of said hub portions; b. a casing having cylindrical intersecting bores rotatably supporting said rotors, end walls bounding said bores axially and low and high pressure ports for passing the working fluid into said bores; c. said rotors being rotatable in said bores with the teeth in sealing proximity to the walls thereof for positive displacement and change of volume of working fluid moving through the machine during each working cycle; d. the tooth on the main rotor having a tip and a first flank and a second flank, said second flank having a convex portion and a portion merging with the hub portion; e. the tooth of the gate rotor having a concave flank generated by the main rotor tooth tip and a second flank, said second flank merging with the hub portion; f. the hub portion of each rotor having a recess located adjacent a tooth flank to permit interengagement when the rotors are rotated; g. the recess of said gate rotor being defined by a convex contour portion extending from the hub portion and merging with a concave contour portion which in turn merges with the concave flank of the gate rotor; h. the hub portion of the gate rotor controlling the high pressure port; i. the rotors having such profiles as to seal the bores and the end walls of the casing during the main part of each revolution and so as to cause the concave flank of the gate rotor tooth and said recess defining convex and concave contour portions to be generated by said main rotor tooth and the convex flank portions thereof along a sweep of substantially 90* of the periphery of the gate rotor, the concave flank of the gate rotor tooth and said convex and concave flank of the gate rotor tooth and said convex and concave contours forming together combined concave and convex contour portions having a single inflection point; j. said profiles further being such that a first sealing line is formed between the main rotor tooth tip and the generated concave flank of the gate rotor tooth and a portion of said concave contour portion of the gate rotor hub during the minor part of each revolution when the teeth interengage, said first sealing line being located farther remote from the axis of rotation of the gate rotor than a second sealing line formed between the convex flank of the main rotor tooth and said recess defining contour portions which are generated by the convex main rotor tooth flank, and k. the profiles of said rotors being calibrated so that a compressed fluid space communicating with the high pressure port will be located between the concave flank of the gate rotor tooth and the convex flank of the main rotor tooth when the teeth interengage and said sealing lines move and until the sealing lines intersect, whereby the torque of the fluid pressure acting on said rotors during each revolution is maintained in the same direction during a complete working cycle of the machine.
 4. A rotary machine according to claim 3, in which the convex main rotor leading tooth flank comprises a convex contour portion extending from the tooth tip and merging with the substantially constant radius hub portion through a flat contour portion, which is tangent to said convex contour portion and said hub portion. 